Packet Tunneling IPv6 over IPv4 protocol 41 (Teredo or 6to4) is nothing new. It was first introduce in RFC 2473 in December 1998 and has been in use since ~2002. Depending of the age of your home router, it may already have some form of IPv6 support. As an example, the Linksys WRT610N router version 1.0 has a hidden page http://router/System.asp that adds support for protocol 41 and this support is listed as Vista Premium.

To check if your router is allowing protocol 41 to flow freely in and out of your home network, you can run a sniffer against the external IP of your router looking for that protocol. You can use either tcpdump or Wireshark to verify. Using tcpdump, you can issues the following command:

Even if you are not setup for IPv6, there may be a lot of interesting data flowing your way. For example, from my router I can see ICMP6 echo requests, TCP traffic attempting to connect to strange ports and of course my own outbound 6to4 traffic. The last 3 traces are a 3-way handshake associated with web traffic connecting to the Wireshark website via IPv6 6to4 tunnel. Note that IP 192.88.188.99 is listed as a 6TO4-RELAY-ANYCAST-IANA-RESERVED address.

If your home router supports some form of IPv6, native, Teredo or 6to4 and would like to share that information, post it via our contact page.